Chemistry: Terms and Description

Topics: Water, Water pollution, PH Pages: 4 (1275 words) Published: May 11, 2014
pH
In chemistry, pH is a measure of the acidity or basicity of an aqueous solution. Solutions with a pH less than 7 are said to be acidic and solutions with a pH greater than 7 are basic or alkaline. Pure water has a pH very close to 7. pH is defined as the decimal logarithm of the reciprocal of the hydrogen ion activity, aH+, in a solution.

Universal indicator consists of a mixture of indicators such that there is a continuous color change from about pH 2 to pH 10. Universal indicator paper is made from absorbent paper that has been impregnated with universal indicator.

Indicator
Low pH color
Transition pH range
High pH color
Thymol Blue(first transition)
Red
1.2 – 2.8
Yellow
Mythyl Red
Red
4.4 – 6.2
Yellow
Bromothymol Blue
Yellow
6.0 – 7.6
Blue
Thymol blue (second transition)
Yellow
8.0 – 9.6
Blue
Phenolphthelein
Colorless
  8.3 – 10.0
Fuchsia

In our lab , we used pH meter to calculate pH of samples. A pH meter is an electronic device used for measuring the pH of a liquid (though special probes are sometimes used to measure the pH of semi-solid substances). A typical pH meter consists of a special measuring probe connected to an electronic meter that measures and displays the pH reading. Color

The Platinum-Cobalt Scale (Pt/Co scale or Apha-Hazen Scale ) is a color scale that was introduced in 1892 by chemist Allen Hazen(1869-1930). The index was developed as a way to evaluate pollution levels in waste water. It has since expanded to a common method of comparison of the intensity of yellow-tinted samples. It is specific to the color yellow and is based on dilutions of a 500 ppm platinum cobalt solution. The ASTM has detailed description and procedures in ASTM Designation D1209, "Standard Test Method for Color of Clear Liquids (Platinum-Cobalt Scale) Electrical Conductivity (EC)

The electrical conductivity of the water depends on the water temperature : the higher the temperature, the higher the electrical conductivity would...
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